Thrall Server - Character: Shincha.
Whenever I open a mailbox to check my mail, the mailbox randomly closes. I had one mail from the auction house, but when I attempted to open it, the letter and the mailbox randomly closed, and I did not receive the gold from the sale. This happened at the Valley of Strength Auction House Mailbox at approximately 3:50 AM PST.
Sounds like an addon issue.
Update: This is happening across all my characters. I am also unable to use the escape key to bring up the menu.
I will turn off addons once the servers are back up and see if that changes anything. Thank you for the suggestion Nok!
Titan Panel - Mail was updated since the last time I played, and it was causing the issue. Everything works now and is accounted for.
I just came here to thank you! It was driving me absolutely insane. Removed Titan Mail and now I am enjoying life again!
You are my literal hero right now lol this was driving me SO NUTS 
Thank Christ you made this post!
Because it was driving me batty as well.
I removed the wrong addons apparently ‘TSM’ ‘Postal’ and issue persisted.
Well its FEB now and Titan Mail still has the same issue. Its been removed now!
I don’t bother with TSM, nor do I have Titan Mail. I do have postal though, and it’s been working fine without any issues. Just in case you’re wary of downloading one or the other.
How good is postal? what does it allow you to do?
It’s just a good mail add-on. Broadcasts what mail I get, the auctions and how much they sold for. Good for managing the mail between all of my alts and all of that good stuff. One button to open all the mail rather than clicking each one. It’s just a convenience add-on more than anything.
Here’s the link to it if you want to check out their description and screenshots:
I logged in to thank you. This has been crazy-making for the last 3 months. Having to constantly reopen the window for every single item in my mail across all characters. And I could never send mail because it would always close before I could complete it. THANK YOU!
Like many other folks, thanks for posting on this! I was going crazy with this issue!
Thank you SOOO much! I was going bananas!
Glad it helped you but this thread is a year old last post was 5 months ago if a post i 2 to 3 weeks old leave them be year or more never more.